Description of the Related Art
Recently, it is proposed to use a heat accumulation type air-conditioning system for creating a latent heat accumulation medium such as cold water or hot water by driving a heat pump (refrigerator) by utilizing cheap electric power during the nighttime hours and mainly using the latent heat accumulation medium for an air-conditioning system for cooling during the daytime hours. The air-conditioning system is an economically improved air-conditioning equipment and can be suitably used as air-conditioning equipment disposed in a multistoried building, industrial plant, or large-scale regional heat supplying plant. Further, in recent years, the cooling load in the daytime hours in summer is rapidly increasing. Therefore, a stable supply of electric power cannot sometimes be attained. The above air-conditioning system which can reduce the electric power consumption in the daytime hours is of great importance in the stable supply of electric power.
This type of heat accumulation system using ice is generally used for air conditioning. This type of heat accumulation system utilizes water as a latent heat accumulation medium (first liquid). The water is used to continuously make sherbet-state ice with high efficiency. That is, a heat accumulation refrigerant (second liquid) cooled to a temperature equal to or lower than 0.degree. C. is used as a cooling medium. The heat accumulation refrigerant is mainly an oily liquid (non-freezing liquid). The heat accumulation refrigerant is injected into water and brought into direct contact with water to effect the heat exchange and make ice.
Therefore, in the above latent heat accumulation system, the heat transfer efficiency is extremely high and fine ice particles can be obtained. The fine ice particles move upward due to the buoyancy thereof. Thus, the non-freezing liquid is always set in contact with water at 0.degree. C. and the ice making operation is repeated. Therefore, the ice making efficiency is high.
As a conventional latent heat accumulation system in which sherbet-state ice is made by direct contact, a latent heat accumulation system shown in FIG. 1 cited from U.S. Pat. No. 2,996,894 or a latent heat accumulation system shown in FIG. 2 cited from Japanese Patent Disclosure No. 2-97845 are provided, for example.
The latent heat accumulation system shown in FIG. 1 includes a container 10A, oil 10B, water 10C and ice 10D stored in the container 10, nozzle 10E, oil circulating system 10F, refrigerator 10G, pump 10H, stirrer 10I, a cold fluid discharge portion 10J and the like.
The latent heat accumulation system shown in FIG. 2 includes an ice making container 20A, heat storage tank 20B, water 20C, oil 20D having a small specific gravity, oil 20E having a large specific gravity, ice 20F, communicating pipe 20G, pump 20H, refrigerator 20I, small-specific-gravity oil circulating pipe 20J, a small-specific-gravity oil return pipe 20K, water return pipe 20L, float 20M, pump 20N and the like.
In the latent heat accumulation system shown in FIGS. 1 and 2, water is used as the first liquid and an oily liquid which is lighter than water is used as the second liquid. The second liquid which is cooled by the refrigerator is fed via the pump and pipe and injected into water stored in the bottom portion of the water reservoir.
However, with the above structure, since the density of the second liquid which is a non-freezing liquid is almost the same as that of water or the second liquid is lighter than water, the oily liquid will be mixed into the ice made in the sherbet state. As a result, it becomes difficult to draw out cold water directly from the water tank and supply the cold water to the cooling load. Further, it becomes necessary to use a cold transferring heat exchanger in order to transfer the cold from the water tank. Therefore, the requirements for drawing out the cold in a short period of time, making the construction of the device simple and directly drawing out water cannot be met with full satisfaction.
As a latent heat accumulation system made for solving the above problem, a system shown in FIG. 3 cited from Japanese Patent Disclosure No. 56-25664 is proposed, for example. The latent heat accumulation system shown in FIG. 3 includes a water tank 30A, water 30B, oil 30C, an oil supplying device 30D, separation film 30E, return port 30F for circulating water, pump 30G, refrigerator 30H, outlet port 30I for cold water and the like.
In the latent heat accumulation system of FIG. 3, a first liquid (water) is stored in the water tank. A second liquid (which is an oily liquid and is lighter than water and ice) is injected from the bottom portion of the water tank into the first liquid in the upward direction. The second liquid is cooled to a temperature lower than the freezing or solidifying point of the first liquid (water) by the refrigerator. Thus, heat exchange occurs when the second liquid is brought into direct contact with the water. The water is partly frozen and the second liquid moves upwardly in the partly frozen water. In this respect, the condition is the same as that of FIG. 1. Further, the separation film (corelesser) is disposed in the upper portion. The separation film permits the passage of the second liquid (oily liquid) but inhibits the passage of ice. Thus, the amount of use of the oily liquid or second liquid is relatively reduced.
The outlet port is disposed below the separation film. In the bottom portion of the water tank, the cold water outlet port is disposed. With this arrangement, the first liquid which is warmed by absorbing heat from the cooling load can be circulated. Further, it is possible to draw out water directly from the water tank.
However, with the above structure, a problem exists in that emulsion of the second liquid occurs in the process of injecting into the water and a further problem that the second liquid flows into the air-conditioning load may also occur. That is, separation of the first liquid from the second liquid is imperfect.
In general, when an oily liquid is used as the second liquid, the second liquid injected into the first liquid is set into the emulsion state or turbid state. For this reason,, it sometimes takes a long time for the second liquid to be separated from the first liquid. Therefore, it may become necessary to draw out the second liquid by use of a heat exchanger, making it necessary to use a large-scale device.
For the above-described reason, the above system cannot be conveniently used and is not generally accepted by the users although the ice making efficiency thereof is high.
In a heat accumulation system shown in FIG. 4 cited corresponding to Japanese Patent Disclosure No. 1-244225, a heat accumulation system shown in FIG. 5 corresponding to Japanese Patent Disclosure No. 2-110231 and a heat accumulation system shown in FIG. 6 corresponding to Japanese Patent Disclosure No. 3-140767, a liquid having a specific gravity larger than that of the first liquid is used as the second liquid.
The heat accumulation system shown in FIG. 4 includes an ice making tank 40A, heat accumulation tank 40B, water 40C, heat exchanger 40D, water supply pipe 40E, ice 40F, circulating system 40G, ice making liquid 40H and the like.
The heat accumulation system shown in FIG. 5 includes an ice making tank 50A, heat accumulation tank 50B, water 50C, oil 50D, air 50E, ice 50F, circulating system 50G, return path 50H, communicating pipe 50I and the like.
The heat accumulation system shown in FIG. 6 includes a water tank 60A, water 60B, oil 60C, ice 60D, cold transferring section 60E, cooling system 60F and the like.
In the heat accumulation systems shown in FIGS. 4 to 6, the second liquid is stored in the bottom portion of the water tank. The second liquid is cooled by a heat exchanger or refrigerator. Water or the first liquid is injected into the second liquid which is cooled from the bottom portion of the water tank (FIGS. 4 and 6). The boundary portion between the first and second liquids is stirred to change ice formed in the boundary portion into fine ice particles (FIG. 5). In this system, the temperature of the second liquid introduced into the refrigerator becomes relatively lower than that of the freezing or solidifying point (0.degree. C. in the case of water) of the first liquid. Further, in the above systems, a problem occurs in that the freezing efficiency cannot be enhanced although a high heat transfer characteristic can be attained by the direct contact between the first and second liquids occurs.
In order to solve the above problem, a latent heat accumulation system shown in FIG. 7 cited from Japanese Patent Disclosure No. 3-140767 is proposed. The latent heat accumulation system shown in FIG. 7 includes a water tank 70A, water 70B, oil 70C, ice 70D, cold transferring section 70E, cooling system 70F and the like.
In the latent heat accumulation system shown in FIG. 7, the second liquid is collected from the bottom portion of the water tank. The second liquid is cooled to a temperature equal to or lower than the freezing or solidifying point of the first liquid (water) by the refrigerator. The cooled second liquid is poured from a portion in the air into the water tank. In this case, while the second liquid (oily liquid) which is heavier than water drops and is deposited in the water, it sufficiently exchanges heat with the water. The temperature of the second liquid is raised to substantially the water temperature by the time the second liquid is collected from the bottom portion of the water tank. Therefore, the freezing efficiency of the second liquid can be held high.
However, in this system, hard and heavy ice blocks are formed. Generally, such ice blocks are deposited in the boundary portion between the first and second liquids and cannot rise to the surface. The same problem occurs in the systems of FIGS. 4, 5 and 6.